Hi there!My name is ***** ***** I would be happy to help you with your question about your dog.Sorry it has taken someone so long to get back with you, did you still need assistance with your question (I see it's been about 4 hours since you submitted your question)?If so, do you mind telling me when you applied the flea and tick treatment?Just to verify the active ingredients, is this a fipronil and s-methoprene formula?Did your boy have a large number of fleas?How long has the twitching been going on?